Numerous labels and forms are printed each day for a variety of purposes. The printed labels may be attached to envelopes or other packages to indicate the source or destination of the envelope or package as well as any other handling information related to the particular package. For example, the U.S. Postal Service, Federal Express and other delivery services prepare individual labels for each letter or package to be delivered which indicate the addresses of both the source and the recipient, a tracking number and other relevant shipping information. Printed labels may also be applied to boxes, crates or other containers for purposes of inventory control and tracking. Such labels generally identify the type and quantity of goods in the container as well as the location of the container.
In order to print the large number of labels required, devices for rapidly printing large numbers of labels have been developed. These printing devices generally draw a continuous strip of labels from a wound roll and feed the labels past a print head such that predetermined information may be imprinted upon the individual labels. The operator may thereafter remove the printed labels and apply them to the corresponding packages.
Such printing devices include both stationary printing devices which are generally relatively large and portable printing devices which are relatively small so as to be carried by an operator in the field or through a warehouse. Such portable printers include not only the print head and means for entering data, such as a keypad, but also a wound roll of labels and the feed mechanism for drawing labels from the wound roll. Thus, labels may be printed on demand and applied to packages or containers in the field without the operator having to return to a stationary printing device in order to print the desired labels. For example, after counting the number of items in a particular container, an operator of a portable printing device may enter data representative of the type, quantity and location of the items, such as via a keypad, into the portable printer, print a label displaying such data and apply the label to the container.
The information to be imprinted on the labels is provided to the printing device from any one of several sources, including manual entry of the data via a keypad or downloading of data from a control computer. The information, regardless of its source, is imprinted upon the labels by a variety of methods including serial dot matrix printing, thermal printing, laser printing, impact matrix printing, ink jet printing, impact full form printing or other electrographic printing methods.
To further facilitate the rapid printing and processing of labels, labels have been specifically developed to be printed by such label printing devices. These labels, which are generally supplied in a wound roll, typically have an adhesive backing and are releasably supported by a carrier web or liner. In particular, a layer of a release agent, such as silicone, is generally disposed between the adhesive backing and the carrier web to permit removal of the labels from the carrier web.
In operation, the wound roll of labels and the supporting carrier web are rotatably supported by the printing device. The label strip is drawn from the roll and sequentially fed past a print head to imprint the desired information. The label strip is drawn from the wound roll and fed past the print head by a feed mechanism, such as one or more aligned rollers. Once printed, the labels are removed from the carrier web, such as by passing the label strip about a roller having a relatively small diameter, so as to permit application of the imprinted labels to a package. With respect to stationary printing devices, the remaining carrier web may thereafter be wound upon a take-up reel for subsequent disposal.
The carrier web remaining once the labels have been printed and removed is not reused, but is scrap which must be discarded. Even the disposal of the scrap carrier web is problematic, however, since the carrier web contains silicone which requires a relatively long time to degrade. Further, it is estimated that the cost of the carrier web amounts to 20% to 30% of the original cost of the wound roll of labels, thus, significantly increasing the material cost of the labels.
In addition, the carrier web contributes substantially to the overall size of the wound roll of labels. Since portable printing devices are relatively compact and may accordingly only accommodate a wound roll of labels of a predetermined size, the carrier web limits the number of labels which may be included within a portable printing device at any one time. Furthermore, the disposal of carrier web remaining after the labels have been removed is an even greater problem with respect to portable printing devices since such portable printers do not generally include a take-up reel for storing the remaining carrier web for subsequent disposal. Instead, the remaining carrier web must typically be periodically separated from the remainder of the wound roll of labels and disposed of or otherwise stored by the operator to prevent excessive amounts of the scrap carrier web from extending from and accumulating adjacent to the portable printer.
Accordingly, linerless labels have been developed which do not include a supporting carrier web. These labels have a primary substrate which is coated with a layer of adhesive on one side. Further, if these labels are formed in a strip which is to be wound in a roll, a layer of a release agent, such as silicone, is applied to a second side of the primary substrate, opposite the adhesive layer, so as to permit wound roll of labels to be unwound during printing.
However, conventional label printing machines, including conventional portable printing devices, are not adapted to process labels or strips of labels which are not supported by a carrier web. Correspondingly, the adhesive backed labels adhere to the feed mechanism of the printing device. Consequently, the printed labels may not be readily withdrawn from the printing device.
An apparatus for printing a linerless label strip having an adhesive backing which is not supported by a carrier web is disclosed in copending U.S. patent application Ser. No. 08/180,050 (hereinafter the "'050 application") to David M. Uland filed on Jan. 11, 1994 and assigned to the assignee of the present application, the contents of which are incorporated herein by reference. The printing apparatus of the '050 application includes an endless belt for transporting the label strip between a print head and an underlying platen and for permitting withdrawal of the label strip from the printing apparatus after the label strip has been imprinted. While the printing apparatus of the '050 application represents a great advance in the art of printing linerless media, the printing apparatus of the '050 application does require a rotating endless belt for transporting the label strip.
Another apparatus for printing a linerless label strip having an adhesive backing which is not supported by a carrier web is disclosed in copending U.S. application Ser. No. 08/243,198 (hereinafter the "'198 application") to David M. Uland filed on May 16, 1994 and also assigned to the assignee of the present application. The printing apparatus of the '198 application includes a platen roller rotatably mounted to a support frame for supporting and advancing the label strip and a pick for stripping or separating the printed label strip from the platen roller. Thus, a label strip may be fed from a wound roll between a platen roller and an aligned print head such that predetermined indicia are imprinted thereon. Upon further rotation of the platen roller, the leading edge of the label strip engages the pick which acts to release any appreciable adherence between the adhesive backing of the label strip and the platen roller such that the printed labels can extend from and be readily withdrawn from the printing apparatus.
The pick of the printing apparatus of the '198 application generally includes a first edge extending parallel to the axis of the platen roller and typically positioned immediately adjacent to the peripheral surface of the platen roller at a location downstream of the print head. In one embodiment, the first edge is positioned about 90.degree. about the arc of the peripheral surface of the platen roller from the print head. The pick can also include a pick surface extending outwardly from the first edge in a direction away from the platen roller. The pick surface extends generally outwardly from the first edge at an angle of about 30.degree. with respect to a radial line of the platen roller which passes through the first edge. The pick surface can also include a plurality of grooves which extend in a direction away from the platen roller to reduce the surface area of the pick surface which contacts the advancing label strip. The present application is a continuation-in-part of the '198 application, the contents of which are expressly incorporated herein, and is directed to other embodiments of a printing apparatus for printing an adhesive backed label which include means for stripping a leading edge portion of the label strip from the platen roller.